Devices for inspecting the inner side of a pipe generally comprise a casing, inside which is mounted a camera having a forward-looking view and a separate light source. The device is fixed to one end of a semi-rigid rod, which is pushed down a pipe to be inspected. The rod encloses wires for supply of electrical power to the device from a supply outside the pipe and at the same time image signals from the camera to a monitor outside the pipe. On pushing the camera along the pipe, the casing with the camera tends to rotate about its longitudinal axis, so that the image displayed on the monitor is similarly rotated, which makes it difficult to determine the orientation of an image.
To maintain the attitude of the camera it is suggested in U.S. Pat. No. 6,611,661 B1 (Buck) and US 2005/0275725 A1 (Olsson et al.) to make the camera self-leveling by using a leveling weight and mount the camera and the weight freely rotatable within the housing, such that gravitational forces maintain the rotational orientation (attitude) of the camera independent of the housing. None of these two documents discloses the use of a second camera directed to permit closer inspection of an inner surface of the pipe.
A pipe inspection device having two cameras, one for looking forward and one for looking sideways to inspect the inner wall of the pipe fore closely is disclosed in GB 2 342 419 A (Pearpoint Ltd.). The two cameras form an assembly that is rotatable around the longitudinal axis inside the housing, and the sideways looking camera is directed strictly sideways, at a right angle to the longitudinal axis of the housing, and to make it possible for the camera to see the pipe wall, the housing has a circumferential window. The rotation is accomplished by a motor provided inside the casing and, if desired, a sensor may be provided for driving the motor in response to changes in the attitude of the device.
To protect this circumferential window from getting scratched or mechanically damaged in some other way during use of the inspection device, the outer diameter of the window is recessed in comparison with the outer diameter of adjacent portions of the housing. However, to form such a recess, the diameter of adjacent portions of the housing have to be increased, which is a drawback, since it is desirable to make the diameter of the housing as small as possible. Further, such a recess will increase the risk of the inspection device getting stuck in the pipe during inspection thereof, and the recess will also be exposed to accumulation of dirt therein, and irrespective of any rotation of the camera, the rotatable camera cannot inspect pipe surface areas hidden behind the accumulated dirt on the window.
In addition, the camera assembly may require a rotation of up to 180° from a normal top position in order to inspect an area at the bottom of the pipe, and every rotation is time-consuming, even if the rotation is smaller than 180°. To cover an entire pipe a full rotation of 360° may be required.
In addition, the camera assembly may require a rotation of up to 180° from a normal top position in order to inspect an area at the bottom of the pipe, and every rotation is time-consuming, even if the rotation is smaller than 180°.